This application seeks to understand the nature of cerebral arterial constriction following subarachnoid hemorrhage in patients with ruptured intracranial aneurysms. It specifically will examine the nature of spasmogenic substances in blood and cerebrospinal fluid that develop following subarachnoid hemorrhage. Fresh blood contains several contractile substances which gradually decay after several days of hemolysis. However, with later hemolysis blood recovers its contractile character and this study intends to identify the factors in hemolysing blood that account for this vasoactivity. These studies will be carried out in animals, and in patients with ruptured intracranial aneurysms. This research will also attempt to determine whether vasoactivity of blood varies from patient to patient and whether this variation can account for the development of cerebral ischemia. In addition the applicants wish to continue a randomized clinial trial of patients with subarachnoid hemorrhage in an effort to determine whether therapy to reduce vasoactivity will reduce the incidence of cerebral ischemia.